Those low maps drop in addition to higher maps, they're not replacing them.

I've had 26 map dry streak without equal or higher map and then again 8 higher maps in single bad blue.

So that begs the question: why even waste currency on maps if IIQ doesn't even seem to affect map drops?

If you spend a shitton of currency rolling a map to 100%IIQ+, it should at least have a fucking good chance of dropping high-level maps. From my experience, I've run many 100%IIQ+ maps and have gotten 3-4 maps in a row with no map drops at all, or a couple of low-level (pity) map drops. Soon, my "map pool" is obliterated. And, like you, I've also run some "fuck-it" ~30%IIQ blue maps, where 5+ maps would drop.

There was a thread created maybe 2 months ago where a guy documented his map drop stats when he leveled from 99-100, and found that insanely high IIQ (120%+) did shit all when it came to map drops.